Three-dimensional ultrasound image generation apparatus, three-dimensional ultrasound image generation method, and three-dimensional ultrasound image generation program

ABSTRACT

A three-dimensional ultrasound image generation apparatus includes: an image acquisition unit that acquires a plurality of two-dimensional ultrasound images from each of a first viewpoint and a second viewpoint; a probe position information acquisition unit that acquires, for each imaging, position information of an ultrasound probe; a three-dimensional ultrasound image generation unit that generates three-dimensional ultrasound images; an organ extraction unit that extracts an organ included in the three-dimensional ultrasound images; an image processing unit that extracts an unclear image region from the three-dimensional ultrasound image from which at least the organ is extracted based on position information of the organ and the position information of the ultrasound probe and that performs suppression processing of suppressing unclearness; and an image combination unit that generates a combined three-dimensional ultrasound image by combining the three-dimensional ultrasound images from two viewpoints including the three-dimensional ultrasound image on which the suppression processing is performed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of PCT International Application No.PCT/JP2020/016817 filed on Apr. 17, 2020, which claims priority under 35U.S.C § 119(a) to Japanese Patent Application No. 2019-106449 filed onJun. 6, 2019. Each of the above application(s) is hereby expresslyincorporated by reference, in its entirety, into the presentapplication.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to a three-dimensional ultrasound imagegeneration apparatus, a three-dimensional ultrasound image generationmethod, and a three-dimensional ultrasound image generation program forgenerating a three-dimensional ultrasound image.

2. Description of the Related Art

In recent years, with advancements in medical apparatuses such as acomputed tomography (CT) apparatus, a magnetic resonance imaging (MRI)apparatus, and an ultrasound diagnosis apparatus, image diagnosis usinghigher quality and higher resolution medical images has become possible.In the ultrasound diagnosis apparatus, there is known a technique ofgenerating a three-dimensional ultrasound image from two-dimensionalultrasound images which are acquired by performing imaging by anultrasound probe and imaging positions of the ultrasound probe. Thetwo-dimensional ultrasound image may include an unclear image region dueto an artifact caused by reflection and refraction of an ultrasoundwave, a decrease in resolution of an image in proportion to a distancefrom the ultrasound probe, or the like. In diagnosis using theultrasound images, for example, in a case where an imaging target is ablood vessel such as a carotid artery, a thickness of a vascular wall ismeasured. However, in a case where an unclear image region is includedin the ultrasound image, it is difficult to measure a thickness of thevascular wall. In the related art, by imaging an observation target fromdifferent viewpoints, two-dimensional ultrasound images from differentviewpoints are acquired. In this case, in the two-dimensional ultrasoundimages from each of the different viewpoints, by using image regionsother than the unclear image region, a thickness of the vascular wall ismeasured.

On the other hand, in a case where a three-dimensional ultrasound imageis generated using two-dimensional ultrasound images including anunclear image region, similarly, the three-dimensional ultrasound imagealso includes an unclear image region. Similarly, the three-dimensionalultrasound image including an unclear image region is not suitable formeasuring a thickness of the vascular wall. For this reason, in recentyears, there has been disclosed a technique for generating ahigher-definition ultrasound image in which an unclear image region issuppressed.

JP2007-236681A discloses a method of removing an artifact by preparing aplurality of images, which have different positional relationships andinclude images including an artifact and images not including anartifact, and adding or subtracting pixel values of the plurality ofimages. In addition, JP5361166B proposes a method of suppressing imagedistortion due to an artifact by masking a pixel of which an angle froma normal line passing through a center of an element plane of anultrasound probe exceeds an allowable angle and which corresponds to ascanning line by an ultrasound wave, the ultrasound probe being a devicein which a plurality of ultrasound transducers are arranged. Further,JP2003-088521A discloses a method of removing or suppressing an artifactby combining images in different angle ranges in accordance with acoordinate system. Thus, even in a case where an image in one anglerange includes, for example, an artifact caused by multiple reflections,when images in other angle ranges do not include an artifact, theartifact can be removed or suppressed.

SUMMARY OF THE INVENTION

However, in the techniques described in JP2007-236681A, JP5361166B, andJP2003-088521A, an organ to be measured is not extracted. As a result,in an image, it is difficult to suppress an unclear image region due toan artifact caused by an organ to be measured.

The present disclosure has been made in view of the above circumstances,and an object of the present disclosure is to generate ahigher-definition three-dimensional ultrasound image by suppressing anunclear image region caused by an organ to be measured.

According to a first aspect of the present disclosure, there is provideda three-dimensional ultrasound image generation apparatus including: animage acquisition unit that acquires a plurality of two-dimensionalultrasound images from each of a first viewpoint and a second viewpointby imaging a target organ in a subject at a plurality of imagingpositions while moving an ultrasound probe in one direction along a bodysurface of the subject, the plurality of two-dimensional ultrasoundimages being acquired by performing imaging at the plurality of imagingpositions from each of at least two viewpoints of the first viewpointand the second viewpoint; a probe position information acquisition unitthat acquires, for each imaging, position information including animaging direction indicating a direction of the viewpoint of theultrasound probe and the imaging position for each viewpoint; athree-dimensional ultrasound image generation unit that generatesthree-dimensional ultrasound images from each of the first viewpoint andthe second viewpoint based on the plurality of two-dimensionalultrasound images from each of the first viewpoint and the secondviewpoint which are acquired by the image acquisition unit and theposition information for each imaging which is acquired by the probeposition information acquisition unit; an organ extraction unit thatextracts the organ included in the three-dimensional ultrasound imagesbased on at least one three-dimensional ultrasound image among thethree-dimensional ultrasound images from each of the first viewpoint andthe second viewpoint; an image processing unit that extracts an unclearimage region from the three-dimensional ultrasound image from which atleast the organ is extracted among the three-dimensional ultrasoundimages from each of the first viewpoint and the second viewpoint, basedon position information of the organ extracted by the organ extractionunit and the position information of the ultrasound probe which isacquired by the probe position information acquisition unit, and thatperforms suppression processing of suppressing unclearness in theextracted image region; and an image combination unit that generates acombined three-dimensional ultrasound image by combining thethree-dimensional ultrasound images from two viewpoints of the firstviewpoint and the second viewpoint, the three-dimensional ultrasoundimage on which the suppression processing is performed being included inthe three-dimensional ultrasound images from at least one viewpointamong the three-dimensional ultrasound images from the two viewpoints.

According to a second aspect of the present disclosure, there isprovided a three-dimensional ultrasound image generation apparatusincluding: an image acquisition unit that acquires a plurality oftwo-dimensional ultrasound images from each of a first viewpoint and asecond viewpoint by imaging a target organ in a subject at a pluralityof imaging positions while moving an ultrasound probe in one directionalong a body surface of the subject, the plurality of two-dimensionalultrasound images being acquired by performing imaging at the pluralityof imaging positions from each of at least two viewpoints of the firstviewpoint and the second viewpoint; a probe position informationacquisition unit that acquires, for each imaging, position informationincluding an imaging direction indicating a direction of the viewpointof the ultrasound probe and the imaging position for each viewpoint; anorgan extraction unit that extracts the organ included in thetwo-dimensional ultrasound images based on at least one two-dimensionalultrasound image among the plurality of two-dimensional ultrasoundimages from at least one viewpoint of the first viewpoint or the secondviewpoint which are acquired by the image acquisition unit; an imageprocessing unit that extracts an unclear image region from each of theplurality of two-dimensional ultrasound images corresponding to theviewpoint of the two-dimensional ultrasound image from which at leastthe organ is extracted among the two-dimensional ultrasound images fromeach of the first viewpoint and the second viewpoint, based on positioninformation of the organ extracted by the organ extraction unit and theposition information of the ultrasound probe which is acquired by theprobe position information acquisition unit, and that performssuppression processing of suppressing unclearness in the extracted imageregion; a three-dimensional ultrasound image generation unit thatgenerates three-dimensional ultrasound images from two viewpoints of thefirst viewpoint and the second viewpoint based on each of the pluralityof two-dimensional ultrasound images from two viewpoints of the firstviewpoint and the second viewpoint, the two-dimensional ultrasound imageon which the suppression processing is performed being included in thetwo-dimensional ultrasound images from at least one viewpoint among thetwo-dimensional ultrasound images from two viewpoints; and an imagecombination unit that generates a combined three-dimensional ultrasoundimage by combining the three-dimensional ultrasound images from twoviewpoints of the first viewpoint and the second viewpoint which aregenerated by the three-dimensional ultrasound image generation unit.

In the present disclosure, the viewpoints may be two viewpoints or threeor more viewpoints as long as the first viewpoint and the secondviewpoint are included.

Further, in the three-dimensional ultrasound image generation apparatusaccording to the aspect of the present disclosure, the image processingunit may extract the unclear image region based on a traveling directionof an ultrasound wave emitted from the ultrasound probe to the organ,the traveling direction of the ultrasound wave being derived based onthe position information of the organ extracted by the organ extractionunit and the position information of the ultrasound probe.

Further, in the three-dimensional ultrasound image generation apparatusaccording to the aspect of the present disclosure, the image processingunit may extract, as the unclear image region, a region in which anangle formed by the traveling direction of the ultrasound wave and anouter front surface of the organ is equal to or smaller than apredetermined threshold value.

Further, in the three-dimensional ultrasound image generation apparatusaccording to the aspect of the present disclosure, the suppressionprocessing may be processing of decreasing a pixel value of the unclearimage region to be relatively lower than pixel values of other regions.

Further, in the three-dimensional ultrasound image generation apparatusaccording to the aspect of the present disclosure, the image combinationunit may perform averaging processing of averaging pixel values ofpixels at the same positions based on the three-dimensional ultrasoundimage from two viewpoints of the first viewpoint and the secondviewpoint, the averaging processing being processing of averaging thepixel values of regions other than the unclear image region on which thesuppression processing is performed.

Further, the three-dimensional ultrasound image generation apparatusaccording to the aspect of the present disclosure may further include adisplay control unit that causes a display unit to display at least oneimage of the two-dimensional ultrasound image or the three-dimensionalultrasound image. The display control unit may control the display unitto display the combined three-dimensional ultrasound image, and maycontrol the display unit to display the two-dimensional ultrasoundimages which are imaged at imaging positions closest to a positiondesignated by a user on the combined three-dimensional ultrasound imagewhich is displayed.

Further, the three-dimensional ultrasound image generation apparatusaccording to the aspect of the present disclosure may further include amarker member that is fixed to the ultrasound probe, and an imagecapturing unit that captures an image of the ultrasound probe and themarker member within the same image capturing range. The probe positioninformation acquisition unit may acquire the position information of theultrasound probe based on a captured image of the ultrasound probe andthe marker member which is acquired by the image capturing unit.

Further, the three-dimensional ultrasound image generation apparatusaccording to the aspect of the present disclosure may further include asix-axis sensor that is provided on the ultrasound probe. The probeposition information acquisition unit may acquire the positioninformation of the ultrasound probe based on output information which isoutput from the six-axis sensor.

Further, the three-dimensional ultrasound image generation apparatusaccording to the aspect of the present disclosure may further include amarker member that is fixed to the ultrasound probe, a six-axis sensorthat is provided on the ultrasound probe, and an image capturing unitthat captures an image of the ultrasound probe and the marker memberwithin the same image capturing range. The probe position informationacquisition unit may acquire the position information of the ultrasoundprobe based on a captured image of the ultrasound probe and the markermember which is acquired by the image capturing unit and outputinformation which is output from the six-axis sensor.

According to a first aspect of the present disclosure, there is provideda three-dimensional ultrasound image generation method including:acquiring a plurality of two-dimensional ultrasound images from each ofa first viewpoint and a second viewpoint by imaging a target organ in asubject at a plurality of imaging positions while moving an ultrasoundprobe in one direction along a body surface of the subject, theplurality of two-dimensional ultrasound images being acquired byperforming imaging at the plurality of imaging positions from each of atleast two viewpoints of the first viewpoint and the second viewpoint;acquiring, for each imaging, position information including an imagingdirection indicating a direction of the viewpoint of the ultrasoundprobe and the imaging position for each viewpoint; generatingthree-dimensional ultrasound images from each of the first viewpoint andthe second viewpoint based on the plurality of acquired two-dimensionalultrasound images from each of the first viewpoint and the secondviewpoint and the acquired position information for each imaging;extracting the organ included in the three-dimensional ultrasound imagesbased on at least one three-dimensional ultrasound image among thethree-dimensional ultrasound images from each of the first viewpoint andthe second viewpoint; extracting an unclear image region from thethree-dimensional ultrasound image from which at least the organ isextracted among the three-dimensional ultrasound images from each of thefirst viewpoint and the second viewpoint, based on position informationof the extracted organ and the acquired position information of theultrasound probe, and performing suppression processing of suppressingunclearness in the extracted image region; and generating a combinedthree-dimensional ultrasound image by combining the three-dimensionalultrasound images from two viewpoints of the first viewpoint and thesecond viewpoint, the three-dimensional ultrasound image on which thesuppression processing is performed being included in thethree-dimensional ultrasound images from at least one viewpoint amongthe three-dimensional ultrasound images from the two viewpoints.

According to a second aspect of the present disclosure, there isprovided a three-dimensional ultrasound image generation methodincluding: acquiring a plurality of two-dimensional ultrasound imagesfrom each of a first viewpoint and a second viewpoint by imaging atarget organ in a subject at a plurality of imaging positions whilemoving an ultrasound probe in one direction along a body surface of thesubject, the plurality of two-dimensional ultrasound images beingacquired by performing imaging at the plurality of imaging positionsfrom each of at least two viewpoints of the first viewpoint and thesecond viewpoint; acquiring, for each imaging, position informationincluding an imaging direction indicating a direction of the viewpointof the ultrasound probe and the imaging position for each viewpoint;extracting the organ included in the two-dimensional ultrasound imagesbased on at least one two-dimensional ultrasound image among theplurality of acquired two-dimensional ultrasound images from at leastone viewpoint of the first viewpoint or the second viewpoint; extractingan unclear image region from each of the plurality of two-dimensionalultrasound images corresponding to the viewpoint of the two-dimensionalultrasound image from which at least the organ is extracted among thetwo-dimensional ultrasound images from each of the first viewpoint andthe second viewpoint, based on position information of the extractedorgan and the acquired position information of the ultrasound probe, andperforming suppression processing of suppressing unclearness in theextracted image region; generating three-dimensional ultrasound imagesfrom two viewpoints of the first viewpoint and the second viewpointbased on each of the plurality of two-dimensional ultrasound images fromtwo viewpoints of the first viewpoint and the second viewpoint, thetwo-dimensional ultrasound image on which the suppression processing isperformed being included in the two-dimensional ultrasound images fromat least one viewpoint among the two-dimensional ultrasound images fromtwo viewpoints; and generating a combined three-dimensional ultrasoundimage by combining the generated three-dimensional ultrasound imagesfrom two viewpoints of the first viewpoint and the second viewpoint.

According to a first aspect of the present disclosure, there is provideda three-dimensional ultrasound image generation program causing acomputer to function as: an image acquisition unit that acquires aplurality of two-dimensional ultrasound images from each of a firstviewpoint and a second viewpoint by imaging a target organ in a subjectat a plurality of imaging positions while moving an ultrasound probe inone direction along a body surface of the subject, the plurality oftwo-dimensional ultrasound images being acquired by performing imagingat the plurality of imaging positions from each of at least twoviewpoints of the first viewpoint and the second viewpoint; a probeposition information acquisition unit that acquires, for each imaging,position information including an imaging direction indicating adirection of the viewpoint of the ultrasound probe and the imagingposition for each viewpoint; a three-dimensional ultrasound imagegeneration unit that generates three-dimensional ultrasound images fromeach of the first viewpoint and the second viewpoint based on theplurality of two-dimensional ultrasound images from each of the firstviewpoint and the second viewpoint which are acquired by the imageacquisition unit and the position information for each imaging which isacquired by the probe position information acquisition unit; an organextraction unit that extracts the organ included in thethree-dimensional ultrasound images based on at least onethree-dimensional ultrasound image among the three-dimensionalultrasound images from each of the first viewpoint and the secondviewpoint; an image processing unit that extracts an unclear imageregion from the three-dimensional ultrasound image from which at leastthe organ is extracted among the three-dimensional ultrasound imagesfrom each of the first viewpoint and the second viewpoint, based onposition information of the organ extracted by the organ extraction unitand the position information of the ultrasound probe which is acquiredby the probe position information acquisition unit, and that performssuppression processing of suppressing unclearness in the extracted imageregion; and an image combination unit that generates a combinedthree-dimensional ultrasound image by combining the three-dimensionalultrasound images from two viewpoints of the first viewpoint and thesecond viewpoint, the three-dimensional ultrasound image on which thesuppression processing is performed being included in thethree-dimensional ultrasound images from at least one viewpoint amongthe three-dimensional ultrasound images from the two viewpoints.

According to a second aspect of the present disclosure, there isprovided a three-dimensional ultrasound image generation program causinga computer to function as: an image acquisition unit that acquires aplurality of two-dimensional ultrasound images from each of a firstviewpoint and a second viewpoint by imaging a target organ in a subjectat a plurality of imaging positions while moving an ultrasound probe inone direction along a body surface of the subject, the plurality oftwo-dimensional ultrasound images being acquired by performing imagingat the plurality of imaging positions from each of at least twoviewpoints of the first viewpoint and the second viewpoint; a probeposition information acquisition unit that acquires, for each imaging,position information including an imaging direction indicating adirection of the viewpoint of the ultrasound probe and the imagingposition for each viewpoint; an organ extraction unit that extracts theorgan included in the two-dimensional ultrasound images based on atleast one two-dimensional ultrasound image among the plurality oftwo-dimensional ultrasound images from at least one viewpoint of thefirst viewpoint or the second viewpoint which are acquired by the imageacquisition unit; an image processing unit that extracts an unclearimage region from each of the plurality of two-dimensional ultrasoundimages corresponding to the viewpoint of the two-dimensional ultrasoundimage from which at least the organ is extracted among thetwo-dimensional ultrasound images from each of the first viewpoint andthe second viewpoint, based on position information of the organextracted by the organ extraction unit and the position information ofthe ultrasound probe which is acquired by the probe position informationacquisition unit, and that performs suppression processing ofsuppressing unclearness in the extracted image region; athree-dimensional ultrasound image generation unit that generatesthree-dimensional ultrasound images from two viewpoints of the firstviewpoint and the second viewpoint based on each of the plurality oftwo-dimensional ultrasound images from two viewpoints of the firstviewpoint and the second viewpoint, the two-dimensional ultrasound imageon which the suppression processing is performed being included in thetwo-dimensional ultrasound images from at least one viewpoint among thetwo-dimensional ultrasound images from two viewpoints; and an imagecombination unit that generates a combined three-dimensional ultrasoundimage by combining the three-dimensional ultrasound images from twoviewpoints of the first viewpoint and the second viewpoint which aregenerated by the three-dimensional ultrasound image generation unit.

According to another first aspect of the present disclosure, there isprovided a three-dimensional ultrasound image generation apparatusincluding: a memory that stores a command to be executed by a computer;and a processor configured to execute the stored command, in which theprocessor is configured to execute processing of acquiring a pluralityof two-dimensional ultrasound images from each of a first viewpoint anda second viewpoint by imaging a target organ in a subject at a pluralityof imaging positions while moving an ultrasound probe in one directionalong a body surface of the subject, the plurality of two-dimensionalultrasound images being acquired by performing imaging at the pluralityof imaging positions from each of at least two viewpoints of the firstviewpoint and the second viewpoint, acquiring, for each imaging,position information including an imaging direction indicating adirection of the viewpoint of the ultrasound probe and the imagingposition for each viewpoint, generating three-dimensional ultrasoundimages from each of the first viewpoint and the second viewpoint basedon the plurality of acquired two-dimensional ultrasound images from eachof the first viewpoint and the second viewpoint and the acquiredposition information for each imaging, extracting the organ included inthe three-dimensional ultrasound images based on at least onethree-dimensional ultrasound image among the three-dimensionalultrasound images from each of the first viewpoint and the secondviewpoint, extracting an unclear image region from the three-dimensionalultrasound image from which at least the organ is extracted among thethree-dimensional ultrasound images from each of the first viewpoint andthe second viewpoint, based on position information of the extractedorgan and the acquired position information of the ultrasound probe, andperforming suppression processing of suppressing unclearness in theextracted image region, and generating a combined three-dimensionalultrasound image by combining the three-dimensional ultrasound imagesfrom two viewpoints of the first viewpoint and the second viewpoint, thethree-dimensional ultrasound image on which the suppression processingis performed being included in the three-dimensional ultrasound imagesfrom at least one viewpoint among the three-dimensional ultrasoundimages from the two viewpoints.

According to another second aspect of the present disclosure, there isprovided a three-dimensional ultrasound image generation apparatusincluding: a memory that stores a command to be executed by a computer;and a processor configured to execute the stored command, in which theprocessor is configured to execute processing of acquiring a pluralityof two-dimensional ultrasound images from each of a first viewpoint anda second viewpoint by imaging a target organ in a subject at a pluralityof imaging positions while moving an ultrasound probe in one directionalong a body surface of the subject, the plurality of two-dimensionalultrasound images being acquired by performing imaging at the pluralityof imaging positions from each of at least two viewpoints of the firstviewpoint and the second viewpoint, acquiring, for each imaging,position information including an imaging direction indicating adirection of the viewpoint of the ultrasound probe and the imagingposition for each viewpoint, extracting the organ included in thetwo-dimensional ultrasound images based on at least one two-dimensionalultrasound image among the plurality of acquired two-dimensionalultrasound images from at least one viewpoint of the first viewpoint orthe second viewpoint, extracting an unclear image region from each ofthe plurality of two-dimensional ultrasound images corresponding to theviewpoint of the two-dimensional ultrasound image from which at leastthe organ is extracted among the two-dimensional ultrasound images fromeach of the first viewpoint and the second viewpoint, based on positioninformation of the extracted organ and the acquired position informationof the ultrasound probe, and performing suppression processing ofsuppressing unclearness in the extracted image region, generatingthree-dimensional ultrasound images from two viewpoints of the firstviewpoint and the second viewpoint based on each of the plurality oftwo-dimensional ultrasound images from two viewpoints of the firstviewpoint and the second viewpoint, the two-dimensional ultrasound imageon which the suppression processing is performed being included in thetwo-dimensional ultrasound images from at least one viewpoint among thetwo-dimensional ultrasound images from two viewpoints, and generating acombined three-dimensional ultrasound image by combining the generatedthree-dimensional ultrasound images from two viewpoints of the firstviewpoint and the second viewpoint.

According to the three-dimensional ultrasound image generationapparatus, the three-dimensional ultrasound image generation method, andthe three-dimensional ultrasound image generation program, it ispossible to generate a higher-definition three-dimensional ultrasoundimage by suppressing an unclear image region caused by an organ to bemeasured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram illustrating a configuration of adiagnosis support system including a three-dimensional ultrasound imagegeneration apparatus according to a first embodiment of the presentdisclosure.

FIG. 2 is a conceptual diagram of the diagnosis support system accordingto an embodiment of the present disclosure.

FIG. 3 is a diagram for explaining an ultrasound probe to which a markermember is fixed.

FIG. 4 is a diagram illustrating an example of an image acquired by animage capturing unit.

FIG. 5 is a diagram for explaining an imaging operation by theultrasound probe.

FIG. 6 is a diagram for explaining imaging of an organ in a subject fromdifferent viewpoints.

FIG. 7 is a diagram for explaining imaging of an organ in a subject fromdifferent viewpoints.

FIG. 8 is a diagram for explaining movement of the marker member 52 in acaptured image.

FIG. 9 is a diagram for explaining an unclear image region.

FIG. 10 is a diagram for explaining suppression processing.

FIG. 11 is a diagram for explaining an unclear image region in athree-dimensional ultrasound image from a first viewpoint.

FIG. 12 is a diagram for explaining processing on a three-dimensionalultrasound image from a second viewpoint.

FIG. 13 is a diagram for explaining combination processing.

FIG. 14 is a diagram for explaining a combined three-dimensionalultrasound image VG.

FIG. 15 is a flowchart illustrating processing performed in the firstembodiment of the present disclosure.

FIG. 16 is a flowchart illustrating processing performed in a secondembodiment of the present disclosure.

FIG. 17 is a diagram illustrating an example of a three-dimensionalultrasound image displayed on a display unit.

FIG. 18 is a diagram illustrating an example of a two-dimensionalultrasound image displayed on a display unit.

FIG. 19 is a diagram for explaining the ultrasound probe including asensor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be describedwith reference to the drawings. FIG. 1 is a schematic block diagramillustrating a configuration of a diagnosis support system to which athree-dimensional ultrasound image generation apparatus according to anembodiment of the present disclosure is applied. As illustrated in FIG.1, a diagnosis support system 1 includes a three-dimensional ultrasoundimage generation apparatus 10 according to the present embodiment, anultrasound probe 50 configured to be connected to the three-dimensionalultrasound image generation apparatus 10, an image capturing unit 60, adisplay unit 30, and an input unit 40.

The three-dimensional ultrasound image generation apparatus 10 isconfigured with a computer including a central processing unit (CPU) 11,a primary storage unit 12, a secondary storage unit 13, an externalinterface (I/F) 14, and the like. The CPU 11 controls the entirethree-dimensional ultrasound image generation apparatus 10. The primarystorage unit 12 is a volatile memory used as a work area or the like inexecution of various programs. As an example of the primary storage unit12, a random access memory (RAM) may be used. The secondary storage unit13 is a non-volatile memory that stores various programs and variousparameters in advance, and a three-dimensional ultrasound imagegeneration program 15 according to an embodiment of the presentdisclosure is installed in the secondary storage unit 13.

The three-dimensional ultrasound image generation program 15 isdistributed by being recorded on a recording medium such as a digitalversatile disc (DVD) or a compact disc read only memory (CD-ROM), and isinstalled in a computer from the recording medium.

Alternatively, the three-dimensional ultrasound image generation program15 may be stored in a storage device of a server computer connected to anetwork or a network storage in a state where access from the outside isallowed, or may be downloaded and installed in a computer according to arequest from the outside.

The three-dimensional ultrasound image generation program 15 is executedby the CPU 11, and thus the CPU 11 functions as an image acquisitionunit 21, a probe position information acquisition unit 22, athree-dimensional ultrasound image generation unit 23, an organextraction unit 24, an image processing unit 25, an image combinationunit 26, and a display control unit 27. Examples of the secondarystorage unit 13 include an electrically erasable programmable read-onlymemory (EEPROM), a flash memory, and the like.

The external I/F 14 controls transmission and reception of variousinformation between the three-dimensional ultrasound image generationapparatus 10 and an external apparatus (not illustrated). The CPU 11,the primary storage unit 12, the secondary storage unit 13, and theexternal I/F 14 are connected to a bus line 16 which is a common routethrough which each circuit exchanges data.

The display unit 30 and the input unit 40 are also connected to the busline 16. The display unit 30 is configured with, for example, a liquidcrystal display or the like. As will be described later, the displayunit 30 displays a two-dimensional ultrasound image acquired by theimage acquisition unit 21 and a three-dimensional ultrasound imagegenerated by the three-dimensional ultrasound image generation unit 23.Further, the display unit 30 displays a captured image acquired by theimage capturing unit 60 to be described. The display unit 30 may beconfigured with a touch panel such that the display unit 30 also servesas the input unit 40. The input unit 40 includes a mouse and a keyboard,and receives various setting input by a user. Further, atransmission/reception unit 17 and the image capturing unit 60 such ascamera are also connected to the bus line 16. The transmission/receptionunit 17 controls transmission and reception of various information toand from the ultrasound probe 50 to be described.

The ultrasound probe 50 is configured to be connected to thethree-dimensional ultrasound image generation apparatus 10. As theultrasound probe 50, for example, a probe for sector scanning, a probefor linear scanning, a probe for convex scanning, and the like may beused. FIG. 2 is a conceptual diagram of the diagnosis support systemaccording to the embodiment of the present disclosure. As illustrated inFIG. 2, the ultrasound probe 50 includes a transducer array 50 a whichis provided at a distal end and in which a plurality of ultrasoundtransducers (not illustrated) are arranged in a one-dimensionaldirection. In the embodiment, an example in which the transducer array50 a includes a plurality of ultrasound transducers one-dimensionallyarranged is described. On the other hand, the present disclosure is notlimited thereto. In the transducer array 50 a, a plurality of ultrasoundtransducers may be two-dimensionally arranged.

In a state where the transducer array 50 a is brought into contact witha body surface of a subject M as a living body, the ultrasound probe 50emits (transmits) an ultrasound wave to a portion of the subject M to bemeasured, and detects (receives) the reflected ultrasound wave which isreflected and returned by the subject M. The ultrasound probe 50converts an electric signal with a pulse wave or a continuous wave thatis output from the transmission/reception unit 17 into an ultrasoundwave, and emits the converted ultrasound wave. Further, the ultrasoundprobe 50 converts the reflected ultrasound wave that is received into anelectric signal, and transmits the converted electric signal to thetransmission/reception unit 17.

The transmission/reception unit 17 transmits, to the ultrasound probe50, an electric signal with a pulse wave or a continuous wave that isfor driving the plurality of ultrasound transducers included in theultrasound probe 50. Further, the transmission/reception unit 17receives a plurality of electric signals generated by the plurality ofultrasound transducers that receive the reflected ultrasound wave. Thetransmission/reception unit generates a reception signal by performingamplification and analog/digital (A/D) conversion on the receivedelectric signal. The reception signal is, for example, a signalincluding a plurality of signals that are arranged in an arrangementdirection of the ultrasound transducers and in a direction which is atransmission direction of the ultrasound wave and which is perpendicularto the arrangement direction of the ultrasound transducers (hereinafter,referred to as a depth direction). Each signal of the plurality ofsignals is a digital signal which represents, as a digital value, anamplitude of the reflected ultrasound wave. The transmission processingand the reception processing are repeatedly and continuously performed,and thus a plurality of pieces of frame data including a plurality ofreception signals are generated.

In the present disclosure, the frame data refers to group data of thereception signals required to configure one tomographic image, a signalwhich is processed to configure tomographic image data based on thegroup data, or one piece of tomographic image data or a tomographicimage which is configured based on the group data. In the presentembodiment, the frame data refers to one piece of tomographic imagedata. The configured tomographic image data is stored in the primarystorage unit 12.

Further, in the present embodiment, a marker member is fixed to theultrasound probe 50. FIG. 3 is a diagram for explaining the ultrasoundprobe 50 to which a marker member is fixed according to an embodiment ofthe present disclosure. In FIG. 3, a portion at which the marker memberis fixed to the ultrasound probe 50 is simply illustrated, unlike anactual shape.

As illustrated in FIG. 3, the ultrasound probe 50 includes a cable 51for connection with the transmission/reception unit 17. Further, amarker member 52 is fixed to an outer circumferential surface of theultrasound probe 50. The marker member 52 includes three sphericalmarkers, that is, a marker 52 x, a marker 52 y, and a marker 52 z, andthree axes of an x-axis, a y-axis, and a z-axis of which axialdirections are orthogonal to each other. The three markers of the marker52 x, the marker 52 y, and the marker 52 z are respectively provided atone ends of the three axes of the x-axis, the y-axis, and the z-axis,with a marker center 52 a as a center of the markers. The other ends ofthe three axes of the x-axis, the y-axis, and the z-axis are provided ona column provided on the ultrasound probe 50. Further, the three markersof the marker 52 x, the marker 52 y, and the marker 52 z are colored,for example, in different colors, and can be identified by the colors.

In the present embodiment, a configuration in which the marker member 52includes the three markers of the marker 52 x, the marker 52 y, and themarker 52 z is described. On the other hand, the technique of thepresent disclosure is not limited thereto, and markers other than thethree markers may be used. For example, four or five markers may beused. Further, the shape of the marker is not limited to a sphericalshape, and may be, for example, a rectangular parallelepiped shape or aconical shape, and may be appropriately changed.

The image capturing unit 60 illustrated in FIG. 2 is provided at aposition at which the ultrasound probe 50 and the marker member 52 canbe captured together within the same image capturing range. FIG. 4 is adiagram illustrating an example of an image acquired by the imagecapturing unit 60. As illustrated in FIG. 4, in an image D acquired bythe image capturing unit 60, the ultrasound probe 50 that is held by ahand H of the user and that is brought into contact with a body surfaceof the subject M and the marker member 52 that is fixed to theultrasound probe 50 appear.

FIG. 5 is a diagram for explaining an imaging operation by theultrasound probe 50. As illustrated in FIG. 5, in a state where theultrasound probe 50 is brought into contact with the body surface of thesubject M by the user, imaging is performed at different positions bymoving the ultrasound probe 50 in a direction indicated by, for example,an arrow S. A plurality of two-dimensional ultrasound images P areacquired at a plurality of different imaging positions at which imagingis performed. The imaging position is a position of the ultrasound probe50 on the body surface for each imaging. The two-dimensional ultrasoundimage P is a tomographic image having a cross section extending in adepth direction from each imaging position to the inside of the subject.

FIG. 6 and FIG. 7 are diagrams for explaining imaging of an organ in thesubject from different viewpoints. In the present embodiment, as anorgan in the subject M, a blood vessel, specifically, a carotid arteryM2, is imaged. As illustrated in FIG. 6, in a state where the ultrasoundprobe 50 is brought into contact with a cervical portion M1 of thesubject M from a front surface side of the subject M (a direction of anarrow V1), the ultrasound probe 50 is moved along the carotid artery M2by the user. Thereby, the carotid artery M2 is imaged at a plurality ofimaging positions. At this time, the ultrasound probe 50 is brought intocontact with the cervical portion M1 such that the arrangement directionof the ultrasound transducers of the ultrasound probe 50 is orthogonalto the carotid artery M2 and a blood flow direction, that is, in adirection indicated by a black region in FIG. 6. Thereby, a minor-axiscross section of a blood vessel in a minor-axis direction of the carotidartery is imaged. Further, the ultrasound probe 50 is brought intocontact with the cervical portion M1 such that the arrangement directionof the ultrasound transducers of the ultrasound probe 50 matches withthe carotid artery M2 and a blood flow direction, that is, in adirection indicated by a shaded region in FIG. 6. Thereby, a major-axiscross section of a blood vessel in a major-axis direction of the carotidartery is imaged. Here, the arrow V1 of the present embodimentcorresponds to a first viewpoint of the present disclosure.

Further, as illustrated in FIG. 7, in a state where the ultrasound probe50 is brought into contact with the cervical portion M1 of the subject Mfrom a left side of the subject M (a direction of an arrow V2), theultrasound probe 50 is moved along the carotid artery M2 by the user.Thereby, the carotid artery M2 is imaged at a plurality of imagingpositions. At this time, the ultrasound probe 50 is brought into contactwith the cervical portion M1 such that the arrangement direction of theultrasound transducers of the ultrasound probe 50 is orthogonal to thecarotid artery M2 and a blood flow direction, that is, in a directionindicated by a black region in FIG. 7. Thereby, a minor-axis crosssection of a blood vessel in a minor-axis direction of the carotidartery is imaged. Further, the ultrasound probe 50 is brought intocontact with the cervical portion M1 such that the arrangement directionof the ultrasound transducers of the ultrasound probe 50 matches withthe carotid artery M2 and a blood flow direction, that is, in adirection indicated by a shaded region in FIG. 7. Thereby, a major-axiscross section of a blood vessel in a major-axis direction of the carotidartery is imaged. Here, the arrow V2 of the present embodimentcorresponds to a second viewpoint of the present disclosure.

Returning to FIG. 2, the image acquisition unit 21 acquirestwo-dimensional ultrasound images P which are imaged by the ultrasoundprobe 50 at a plurality of imaging positions from at least twoviewpoints including the first viewpoint and the second viewpoint. Thetwo-dimensional ultrasound image P is a tomographic image having a crosssection extending in a depth direction from each imaging position to theinside of the subject. The ultrasound probe 50 outputs, to the primarystorage unit 12, the plurality of two-dimensional ultrasound images P(tomographic images) which are imaged. The image acquisition unit 21acquires the two-dimensional ultrasound images P (tomographic images)from the primary storage unit 12.

In each imaging, the probe position information acquisition unit 22acquires position information including an imaging direction indicatinga direction of the viewpoint of the ultrasound probe 50 and an imagingposition for each viewpoint. Specifically, at each of different imagingpositions, the image capturing unit 60 captures the ultrasound probe 50and the marker member 52. A captured image which is obtained bycapturing the ultrasound probe 50 and the marker member 52 is output tothe primary storage unit 12. The probe position information acquisitionunit 22 reads the captured image from the primary storage unit 12. Theprobe position information acquisition unit 22 derives positioninformation including the imaging direction and the imaging position ofthe ultrasound probe 50, from a position of a marker center 52 a, andpositions, sizes, and inclinations of the markers 52 x, 52 y, and 52 zin the captured image, by performing image analysis on the capturedimage which is read. The probe position information acquisition unit 22identifies each of the markers 52 x, 52 y, and 52 z by color. The probeposition information acquisition unit 22 acquires position informationincluding the imaging direction and the imaging position via derivationprocessing.

FIG. 8 is a diagram for explaining movement of the marker member 52 inthe captured image. In a case where the ultrasound probe 50 acquires thetwo-dimensional ultrasound images P at an imaging position T1 and animaging position T2, for example, as illustrated in FIG. 8, the markermember 52 moves in a direction of an arrow T in the captured image. Inthis case, a position of the ultrasound probe 50 in an x direction isderived from an amount of movement of the marker center 52 a in the xdirection. In addition, a position of the ultrasound probe 50 in a ydirection is derived from an amount of change in the sizes of themarkers 52 x, 52 y, and 52 z. Further, an amount of rotation of themarker member 52 is detected from a movement trajectory of the markercenter 52 a of the markers 52 x, 52 y, and 52 z. The direction of theultrasound probe 50, that is, the imaging direction, is derived based onthe amount of rotation. The derived position information including theimaging position and the imaging direction of the ultrasound probe 50 isstored in the primary storage unit 12 by being associated with thetwo-dimensional ultrasound image P which is acquired at the imagingposition. As a method of acquiring the imaging direction and the imagingposition of the ultrasound probe 50 using the marker member 52, a knowntechnique may be used.

The three-dimensional ultrasound image generation unit 23 generates athree-dimensional ultrasound image V for a space determined by an anglerange or a stroke of mechanical scanning of the transducer array 50 aand an electronic scanning range of the transducer array 50 a, by usingthe two-dimensional ultrasound image P acquired by the image acquisitionunit 21 and the position information that is stored in the primarystorage unit 12 by being associated with the two-dimensional ultrasoundimage P and that includes the imaging direction and the imaging positionof the ultrasound probe 50. As a method of generating thethree-dimensional ultrasound image V, a known technique may be used.

The organ extraction unit 24 extracts at least one organ included in thetwo-dimensional ultrasound image P or the three-dimensional ultrasoundimage V, based on the two-dimensional ultrasound image P acquired by theimage acquisition unit 21 or the three-dimensional ultrasound image Vgenerated by the three-dimensional ultrasound image generation unit 23.Here, the organ is not limited to a visceral region such as a heart anda liver. On the other hand, the organ may also include a bone and ablood vessel.

In the present embodiment, an imaging target is a cervical portion. Forthis reason, the organ extraction unit 24 extracts, as a target, a bloodvessel in the three-dimensional ultrasound image V. As a method ofextracting a blood vessel, for example, a method described inJP2010-220742A may be used, the method being a method of obtainingposition information and a main axial direction of a plurality ofcandidate points representing a target tissue having a linear structureand performing reconfiguration such that the plurality of candidatepoints are connected by using a cost function having variables based onthe obtained position information and the obtained main axial direction.Alternatively, a method which is described in JP2011-212314A andautomatically distinguishes and extracts a blood vessel may be used.

Further, a neural network may be used, the neural network being trainedby using, as training data, the two-dimensional ultrasound image P, thethree-dimensional ultrasound image V, and correct answer data of variousorgans so as to output a region representing an organ in a case wherethe two-dimensional ultrasound image P or the three-dimensionalultrasound image V is input.

The image processing unit 25 performs suppression processing ofextracting, based on the position information of the organ extracted bythe organ extraction unit 24 and the position information of theultrasound probe 50 acquired by the probe position informationacquisition unit 22, an unclear image region from the two-dimensionalultrasound image P and the three-dimensional ultrasound image V fromwhich an organ is extracted, and suppressing unclearness in theextracted image region.

The image processing unit 25 extracts an unclear image region based on atraveling direction of the ultrasound wave emitted from the ultrasoundprobe 50 to the organ. First, a case where the organ extraction unit 24extracts an organ based on the three-dimensional ultrasound image Vgenerated by the three-dimensional ultrasound image generation unit 23will be described. FIG. 9 illustrates a diagram for explaining anunclear image region. For convenience of explanation, FIG. 9 illustratesa minor-axis cross section of a blood vessel in a minor-axis directionof the carotid artery M2, that is, a two-dimensional ultrasound image P.On the other hand, the same explanation may be given for athree-dimensional ultrasound image V.

As illustrated in FIG. 9, in a round-shaped organ such as a blood vesselof the carotid artery M2, the ultrasound wave is reflected or refractedon an outer front surface of the organ, specifically, in the vicinity ofa dotted circle indicated by A of FIG. 9. As a result, an artifact islikely to occur. For this reason, the image processing unit 25 performssuppression processing of suppressing unclearness in a region which isan unclear image region and in which an artifact is likely to occur.

FIG. 10 is a diagram for explaining suppression processing. In thepresent embodiment, as illustrated in FIG. 10, the image processing unit25 extracts, as an unclear image region, a region in which an angle αformed by the traveling direction of the ultrasound wave and the outerfront surface of the carotid artery M2 is equal to or smaller than apredetermined threshold value. Specifically, in FIG. 10, as an unclearimage region, a region between the traveling direction of the ultrasoundwave indicated by an arrow and the outer front surface of the carotidartery M2 (in FIG. 10, a region indicated by a shaded region) isextracted. Here, the angle α is a value which is calculated for each ofsizes and types of organs based on a relationship between an anglemeasured in advance and an artifact.

FIG. 11 is a diagram for explaining an unclear image region in athree-dimensional ultrasound image VO1 from the first viewpoint. In FIG.11, for convenience of explanation, one unclear image region will bedescribed below. On the other hand, the same explanation may be giveneven in a case where there are two or more unclear image regions. Asillustrated in a left part of FIG. 11, in the three-dimensionalultrasound image VO1 from the first viewpoint, in a case where the imageprocessing unit 25 extracts an unclear image region A1, as illustratedin a right part of FIG. 11, the image processing unit 25 performsprocessing of deleting the unclear image region A1, and performs thesuppression processing on an image from which the unclear image regionA1 is deleted. Thereby, a three-dimensional ultrasound image VA1 fromthe first viewpoint is generated.

Next, a case where the organ extraction unit 24 extracts an organ basedon the plurality of two-dimensional ultrasound images P acquired by theimage acquisition unit 21 will be described. Even in a case of thetwo-dimensional ultrasound images P, similar to the above-describedthree-dimensional ultrasound image V, as illustrated in FIG. 9, in around-shaped organ such as a blood vessel of the carotid artery M2, theultrasound wave is reflected or refracted on an outer front surface ofthe organ, specifically, in the vicinity of a dotted circle indicated byA of FIG. 9. As a result, an artifact is likely to occur. For thisreason, the image processing unit 25 performs suppression processing ofsuppressing unclearness in a region which is an unclear image region andin which an artifact is likely to occur. Specifically, similar to thecase of the three-dimensional ultrasound image V, as illustrated in FIG.10, the image processing unit 25 extracts, as an unclear image region, aregion in which an angle α formed by the traveling direction of theultrasound wave and the outer front surface of the carotid artery M2 isequal to or smaller than a predetermined threshold value.

The image combination unit 26 generates a combined three-dimensionalultrasound image VG by combining the three-dimensional ultrasound imageVA1 after the suppression processing from the first viewpoint with athree-dimensional ultrasound image VO2 from a second viewpoint. FIG. 12is a diagram for explaining processing on the three-dimensionalultrasound image VO2 from the second viewpoint. The three-dimensionalultrasound image VO2 from the second viewpoint is an image that isimaged in an imaging direction different from the imaging direction inthe first viewpoint. Thus, on the outer front surface of the carotidartery M2 irradiated with the ultrasound wave, a position from thesecond viewpoint is different from a position from the first viewpoint.Therefore, as illustrated in FIG. 12, in the three-dimensionalultrasound image VO2 from the second viewpoint, a region in which anartifact occurs, that is, an unclear image region A2, is at a positiondifferent from a position of the unclear image region A1 of FIG. 11.

The image combination unit 26 performs alignment processing of thecarotid artery M2 included in the three-dimensional ultrasound image VO1from the first viewpoint and the carotid artery M2 included in thethree-dimensional ultrasound image VO2 from the second viewpoint. In thepresent embodiment, as illustrated in a right part of FIG. 12, thealignment processing is performed on the three-dimensional ultrasoundimage VO2 from the second viewpoint, and thus a three-dimensionalultrasound image VA2 after the alignment processing from the secondviewpoint on which the alignment processing is performed is generated.The alignment processing may be performed on the three-dimensionalultrasound image VO1 from the first viewpoint, or may be performed onboth of the three-dimensional ultrasound image VO1 from the firstviewpoint and the three-dimensional ultrasound image VO2 from the secondviewpoint. A known technique can be used for the alignment processing.

FIG. 13 is a diagram for explaining combination processing. Asillustrated in FIG. 13, the image combination unit 26 combines a regionin the three-dimensional ultrasound image VA1 after the suppressionprocessing from the first viewpoint from which the unclear image regionA1 is deleted with a region in the three-dimensional ultrasound imageVA2 after the alignment processing from the second viewpoint thatcorresponds to the deleted region. FIG. 14 is a diagram for explaining acombined three-dimensional ultrasound image VG. In the three-dimensionalultrasound image VA1 after the suppression processing from the firstviewpoint, the unclear image region A1 is deleted. Thus, the unclearimage region does not exist. The three-dimensional ultrasound image VA1after the suppression processing from the first viewpoint from which theunclear image region is deleted is combined with the region other thanthe unclear image region A2 in the three-dimensional ultrasound imageVA2 after the alignment processing from the second viewpoint. Thereby, acombined three-dimensional ultrasound image VG after the combinationprocessing does not include an unclear image region, and is athree-dimensional ultrasound image with definition higher than that ofthe three-dimensional ultrasound image VO1 from the first viewpoint.

Returning to FIG. 2, the display control unit 27 causes the display unit30 to display at least one of the two-dimensional ultrasound image Pwhich is imaged by the ultrasound probe 50 or the three-dimensionalultrasound image V. Further, the display control unit 27 causes thedisplay unit 30 to display the combined three-dimensional ultrasoundimage VG which is combined by the image combination unit 26. The displaycontrol unit 27 may cause one display unit 30 to display at least one ofthe two-dimensional ultrasound image P which is imaged by the ultrasoundprobe 50, the three-dimensional ultrasound image V, or the combinedthree-dimensional ultrasound image VG. In a case where there are twodisplay units 30, each display unit may display the ultrasound images.

Next, processing performed in the present embodiment will be described.FIG. 15 is a flowchart illustrating processing performed in a firstembodiment of the present disclosure.

In a case where the user operates the ultrasound probe 50 in a statewhere the ultrasound probe 50 is brought into contact with the bodysurface of the cervical portion M1 of the subject M, the imageacquisition unit 21 acquires a plurality of two-dimensional ultrasoundimages P that are imaged from a first viewpoint and a second viewpointwhich are different viewpoints (step ST1).

The probe position information acquisition unit 22 acquires, for eachimaging in step ST1, position information including an imaging directionindicating a direction of the viewpoint of the ultrasound probe 50 andan imaging position for each viewpoint (step ST2). The three-dimensionalultrasound image generation unit 23 generates three-dimensionalultrasound images VO1 and VO2 from a first viewpoint and a secondviewpoint (step ST3).

Next, the organ extraction unit 24 extracts a carotid artery M2 includedin the three-dimensional ultrasound image VO1 from the first viewpoint(step ST4). The image processing unit 25 extracts an unclear imageregion in the three-dimensional ultrasound image VO1 from the firstviewpoint, and performs suppression processing of deleting the extractedunclear image region (step ST5).

Next, the image combination unit 26 generates a combinedthree-dimensional ultrasound image VG (step ST6) by combining thethree-dimensional ultrasound image VA1 after the suppression processingfrom the first viewpoint from which the unclear image region is deletedwith the region other than the unclear image region A2 in thethree-dimensional ultrasound image VA2 after the alignment processingfrom the second viewpoint. Thereafter, the process is ended.

As described above, in the present embodiment, the three-dimensionalultrasound image VA1 after the suppression processing from the firstviewpoint from which the unclear image region is deleted is combinedwith the region other than the unclear image region A2 in thethree-dimensional ultrasound image VA2 after the alignment processingfrom the second viewpoint. Thereby, it is possible to generate athree-dimensional ultrasound image in which an unclear image region issuppressed and which has definition higher than that of thethree-dimensional ultrasound image VO1 from the first viewpoint.

In the first embodiment, the plurality of two-dimensional ultrasoundimages P from the first viewpoint and the second viewpoint are acquired,and the three-dimensional ultrasound images V from the first viewpointand the second viewpoint are generated. On the other hand, the techniqueof the present disclosure is not limited thereto. A plurality oftwo-dimensional ultrasound images P from three or more viewpoints may beacquired, and three-dimensional ultrasound images V from the firstviewpoint and the second viewpoint may be generated. In this case, thesuppression processing of suppressing unclearness in an unclear imageregion may be performed only in the three-dimensional ultrasound image Vfrom the first viewpoint, the suppression processing may be performed inthe three-dimensional ultrasound images V from two or more viewpoints,or the suppression processing may be performed in the three-dimensionalultrasound images V from all viewpoints.

Further, in the first embodiment, the organ extraction unit 24 canextract an organ in both of the two-dimensional ultrasound image P andthe three-dimensional ultrasound image V. On the other hand, thetechnique of the present disclosure is not limited thereto. In a casewhere an organ is extracted only in the three-dimensional ultrasoundimage V as in the first embodiment, the organ extraction unit 24 may nothave a function of extracting an organ in the two-dimensional ultrasoundimage P.

Further, in the first embodiment, the organ extraction unit 24 extractsan organ in the three-dimensional ultrasound image V. On the other hand,the organ extraction unit 24 may extract an organ in the two-dimensionalultrasound image P. In this case, the image processing unit 25 performsthe suppression processing on the two-dimensional ultrasound image P.

Next, the three-dimensional ultrasound image generation apparatusaccording to a second embodiment will be described. Thethree-dimensional ultrasound image generation apparatus according to thesecond embodiment performs organ extraction and suppression processingon the two-dimensional ultrasound image P. The three-dimensionalultrasound image generation apparatus according to the second embodimentmay have the same configuration as the three-dimensional ultrasoundimage generation apparatus 10 according to the first embodimentillustrated in FIG. 1. For this reason, a description of theconfiguration will be omitted, and only processing performed in thethree-dimensional ultrasound image generation apparatus according to thesecond embodiment will be described. FIG. 16 is a flowchart illustratingprocessing performed in the second embodiment of the present disclosure.

In a case where the user operates the ultrasound probe 50 in a statewhere the ultrasound probe 50 is brought into contact with the bodysurface of the cervical portion M1 of the subject M, the imageacquisition unit 21 acquires a plurality of two-dimensional ultrasoundimages P that are imaged from a viewpoint 1 and a viewpoint 2 which aredifferent viewpoints (step ST11). The probe position informationacquisition unit 22 acquires, for each imaging in step ST11, positioninformation including an imaging direction indicating a direction of theviewpoint of the ultrasound probe 50 and an imaging position for eachviewpoint (step ST12).

Next, the organ extraction unit 24 extracts a carotid artery M2 includedin each of a plurality of two-dimensional ultrasound images P from thefirst viewpoint (step ST13). The image processing unit 25 extracts anunclear image region in each of the plurality of two-dimensionalultrasound images P from the first viewpoint, and performs suppressionprocessing of deleting the extracted unclear image region (step ST14).Here, as illustrated in FIG. 10, the image processing unit 25 extracts,as an unclear image region, a region between the traveling direction ofthe ultrasound wave indicated by an arrow and the outer front surface ofthe carotid artery M2 (in FIG. 10, a region indicated by a shadedregion) for all of the plurality of two-dimensional ultrasound images Pfrom the first viewpoint.

The three-dimensional ultrasound image generation unit 23 generatesthree-dimensional ultrasound images VO1 and VO2 from the first viewpointand the second viewpoint (step ST15). Here, since the three-dimensionalultrasound image VO1 from the first viewpoint is generated based on theplurality of two-dimensional ultrasound images P after the suppressionprocessing from the first viewpoint, the three-dimensional ultrasoundimage VO1 from the first viewpoint does not include an unclear imageregion. That is, as in the three-dimensional ultrasound image VA1 afterthe suppression processing from the first viewpoint illustrated in theleft part of FIG. 13, in the three-dimensional ultrasound image VO1 fromthe first viewpoint, an unclear image region is deleted.

Next, as illustrated in the right part of FIG. 12, the image combinationunit 26 performs, on the three-dimensional ultrasound image VO2 from thesecond viewpoint, the same alignment processing as in the firstembodiment, and generates a three-dimensional ultrasound image VA2 afterthe alignment processing from the second viewpoint on which thealignment processing is performed. The image combination unit 26generates a combined three-dimensional ultrasound image VG (step ST16)by combining the deleted region in the three-dimensional ultrasoundimage VO1 from the first viewpoint from which the unclear image regionis deleted with the region other than the unclear image region A2 in thethree-dimensional ultrasound image VA2 after the alignment processingfrom the second viewpoint on which the alignment processing isperformed. Thereafter, the process is ended.

As described above, in the second embodiment, an unclear image region ineach of the plurality of two-dimensional ultrasound images P from thefirst viewpoint is extracted, and suppression processing of deleting theextracted unclear image region is performed. The three-dimensionalultrasound image VO1 from the first viewpoint is generated based on theplurality of two-dimensional ultrasound images P from the firstviewpoint on which the suppression processing is performed, and iscombined with the three-dimensional ultrasound image VO2 from the secondviewpoint. As described above, even in a case where the suppressionprocessing is performed on the two-dimensional ultrasound images P, ahigh-definition three-dimensional ultrasound image can be generated asin the first embodiment.

In the second embodiment, the plurality of two-dimensional ultrasoundimages P from the first viewpoint and the second viewpoint are acquired,and the three-dimensional ultrasound images V from the first viewpointand the second viewpoint are generated. On the other hand, the techniqueof the present disclosure is not limited thereto. A plurality oftwo-dimensional ultrasound images P from three or more viewpoints may beacquired, and three-dimensional ultrasound images V from the firstviewpoint and the second viewpoint may be generated. In this case, thesuppression processing of suppressing unclearness in an unclear imageregion may be performed only in the plurality of two-dimensionalultrasound images P from the first viewpoint, the suppression processingmay be performed in the plurality of two-dimensional ultrasound images Pfrom two or more viewpoints, or the suppression processing may beperformed in the plurality of two-dimensional ultrasound images P fromall viewpoints.

Further, in the second embodiment, the organ extraction unit 24 canextract an organ in both of the two-dimensional ultrasound image P andthe three-dimensional ultrasound image V. On the other hand, thetechnique of the present disclosure is not limited thereto. In a casewhere an organ is extracted only in the two-dimensional ultrasound imageP as in the second embodiment, the organ extraction unit 24 may not havea function of extracting an organ in the three-dimensional ultrasoundimage V.

Further, in the first embodiment and the second embodiment, the imagecombination unit 26 may further perform averaging processing ofaveraging pixel values of pixels at the same positions with respect topixel values of regions other than the region on which the suppressionprocessing is performed, based on the three-dimensional ultrasound imageVA1 after the suppression processing from the first viewpoint or thethree-dimensional ultrasound image VO1 generated based on the pluralityof two-dimensional ultrasound images P from the first viewpoint on whichthe suppression processing is performed, and the three-dimensionalultrasound image VA2 after the alignment processing from the secondviewpoint. Thereby, a noise in the image can be reduced, and thus ahigher-definition three-dimensional ultrasound image can be generated.

Further, in the first embodiment and the second embodiment, the imageprocessing unit 25 deletes an unclear image region. On the other hand,the technique of the present disclosure is not limited thereto. Theimage processing unit 25 may decrease a pixel value of the unclear imageregion to be relatively lower than pixel values of other regions. Asprocessing of decreasing a pixel value of the unclear image region, forexample, processing of decreasing a pixel value of the unclear imageregion by setting a weight may be performed. Specifically, for example,processing of averaging a pixel value of the unclear image region and apixel value of an image region other than the unclear image region at aratio of 1:2 may be performed. Further, processing of decreasing a pixelvalue of the unclear image region by setting a weight according to adistance from a starting point of an artifact may be performed.Specifically, for example, processing of decreasing a pixel value of theunclear image region by setting a weight of the unclear image region tobe larger as a distance from the ultrasound probe 50 increases may beperformed. As a distance from the ultrasound probe 50 increases, theresolution of the image is lowered. Thus, by decreasing a pixel value ofa region with lower resolution, the unclear image region may be furthersuppressed.

Further, in the first embodiment and the second embodiment, anembodiment in which one organ is extracted in the three-dimensionalultrasound image V has been described. On the other hand, the techniqueof the present disclosure is not limited to extraction of one organ. Thetechnique described in the first embodiment may be applied to a casewhere two or more organs are extracted. In this case, processing ofextracting and suppressing an unclear image region may be performed oneach of the extracted organs.

Next, the three-dimensional ultrasound image generation apparatusaccording to a third embodiment will be described. The three-dimensionalultrasound image generation apparatus according to the third embodimentmay have the same configuration as the three-dimensional ultrasoundimage generation apparatus 10 according to the first embodimentillustrated in FIG. 1. For this reason, a description of theconfiguration will be omitted, and only different portions will bedescribed. The display control unit 27 of the three-dimensionalultrasound image generation apparatus according to the third embodimentcontrols the display unit 30 to display the three-dimensional ultrasoundimage V, and controls the display unit 30 to display the two-dimensionalultrasound images P from the first viewpoint and the second viewpointwhich are imaged at imaging positions closest to a position designatedby a user on the displayed three-dimensional ultrasound image V.

FIG. 17 is a diagram illustrating an example of the three-dimensionalultrasound image V displayed on the display unit, and FIG. 18 is adiagram illustrating an example of the two-dimensional ultrasound imagesP displayed on the display unit 30. As illustrated in FIG. 17, the userdesignates a certain position (as an example, an end portion of an arrowin FIG. 17) on the combined three-dimensional ultrasound image VGdisplayed on the display unit 30 by, for example, operating the inputunit 40 such as a mouse.

The display control unit 27 extracts imaging positions closest to thedesignated position from the imaging positions stored in the primarystorage unit 12, extracts the two-dimensional ultrasound images P fromthe first viewpoint and the second viewpoint that are stored in theprimary storage unit 12 by being associated with the extracted imagingpositions, and causes the display unit 30 to display the extractedtwo-dimensional ultrasound images P. The two-dimensional ultrasoundimages P from the first viewpoint and the second viewpoint may bedisplayed in parallel on the display unit 30, or may be alternatelydisplayed so as to be switched according to a user's instruction.

As described above, the two-dimensional ultrasound image in which anunclear image region is not suppressed, that is, including an unclearimage region such as an artifact, is displayed on the display unit 30.Thereby, it is possible to perform diagnosis capable of visuallyrecognizing the original image, such as a degree of attenuation of animage signal.

Further, in the first embodiment and the second embodiment, the probeposition information acquisition unit 22 derives information includingthe imaging position and the imaging direction of the ultrasound probe50, from the position of the marker center 52 a, and the positions, thesizes, and the inclinations of the markers 52 x, 52 y, and 52 z in thecaptured image acquired by capturing the ultrasound probe 50 and themarker member 52 via the image capturing unit 60. On the other hand, thetechnique of the present disclosure is not limited thereto.

The probe position information acquisition unit 22 may acquireinformation including the imaging position and the imaging direction ofthe ultrasound probe 50 by using, for example, an augmented reality (AR)marker. The AR marker is an image including figures having a fixedpattern. The AR marker is provided on the outer circumferential surfaceof the ultrasound probe 50. By using a known program of detecting aposition and a direction of the marker based on image data of theultrasound probe 50 that includes the AR marker captured by the imagecapturing unit 60, the AR marker, that is, the information including theimaging position and the imaging direction of the ultrasound probe 50,may be acquired.

Further, instead of the marker member 52, a projection portion and arecess portion may be provided on a main body of the ultrasound probe50. In this case, information including the imaging position and theimaging direction of the ultrasound probe 50 may be derived by using, asmarkers, the projection portion and the recess portion. In the techniqueof the present disclosure, the marker may have any shape and any form aslong as the marker can be used as an index for defining the imagingposition and the imaging direction of the ultrasound probe 50, and isnot particularly limited.

Further, for example, the diagnosis support system 1 may include asensor instead of the image capturing unit 60 and the marker member 52.

FIG. 19 is a diagram for explaining the ultrasound probe including asensor. In FIG. 19, attachment of a sensor to the ultrasound probe 50 issimply illustrated, unlike the actual shape.

As illustrated in FIG. 19, the ultrasound probe 50 includes a sensor 70attached to the outer circumferential surface of the ultrasound probe50. The sensor 70 is a six-axis sensor that can detect a movingdirection, a direction, and a rotation and can further calculate amoving distance, a moving speed, and the like. The six-axis sensor isrealized by combining an acceleration sensor that can detect threedirections of a direction of front and back, a direction of right andleft, and a direction of up and down with a geomagnetic sensor that candetect directions of north, south, east, and west, or combining anacceleration sensor with a gyro sensor that can detect a speed ofrotation.

The probe position information acquisition unit 22 can acquire theimaging position based on output information which is output from thesensor 70.

In the embodiment, the sensor 70 is provided instead of the imagecapturing unit 60 and the marker member 52. On the other hand, thetechnique of the present disclosure is not limited thereto. The sensor70 may be provided in addition to the image capturing unit 60 and themarker member 52. In this case, the sensor 70 is suitable for detectingthe imaging direction of the ultrasound probe 50, and a method ofcalculating the imaging position from the captured image acquired bycapturing the ultrasound probe 50 and the marker member 52 via the imagecapturing unit 60 is suitable for detecting a parallel movement of theultrasound probe 50. Thus, by using the image capturing unit 60, themarker member 52, and the sensor 70, the probe position informationacquisition unit 22 can acquire the imaging position and the imagingdirection with higher accuracy.

Further, in the above-described embodiment, for example, the followingvarious processors may be used as a hardware structure of processingunits performing various processing, such as the image acquisition unit21, the probe position information acquisition unit 22, thethree-dimensional ultrasound image generation unit 23, the organextraction unit 24, the image processing unit 25, the image combinationunit 26, and the display control unit 27. The various processorsinclude, as described above, a CPU, which is a general-purpose processorthat functions as various processing units by executing software(programs), and a dedicated electric circuit, which is a processorhaving a circuit configuration specifically designed to execute aspecific processing, such as a programmable logic device (PLD) or anapplication specific integrated circuit (ASIC) that is a processor ofwhich the circuit configuration may be changed after manufacturing suchas a field programmable gate array (FPGA).

One processing unit may be configured by one of these variousprocessors, or may be configured by a combination of two or moreprocessors having the same type or different types (for example, acombination of a plurality of FPGAs or a combination of a CPU and anFPGA). Further, the plurality of processing units may be configured byone processor.

As an example in which the plurality of processing units are configuredby one processor, firstly, as represented by a computer such as a clientand a server, a form may be adopted in which one processor is configuredby a combination of one or more CPUs and software and the processorfunctions as the plurality of processing units. Secondly, as representedby a system on chip (SoC) or the like, a form may be adopted in which aprocessor that realizes the function of the entire system including theplurality of processing units by one integrated circuit (IC) chip isused. As described above, the various processing units are configured byusing one or more various processors as a hardware structure.

Further, as the hardware structure of the various processors, morespecifically, an electric circuit (circuitry) in which circuit elementssuch as semiconductor elements are combined may be used.

EXPLANATION OF REFERENCES

-   -   1: diagnosis support system    -   10: three-dimensional ultrasound image generation apparatus    -   11: CPU    -   12: primary storage unit    -   13: secondary storage unit    -   14: external I/F    -   15: three-dimensional ultrasound image generation program    -   16: bus line    -   17: transmission/reception unit    -   21: image acquisition unit    -   22: probe position information acquisition unit    -   23: three-dimensional ultrasound image generation unit    -   24: organ extraction unit    -   25: image processing unit    -   26: image combination unit    -   27: display control unit    -   30: display unit    -   40: input unit    -   50: ultrasound probe    -   50 a: transducer array    -   51: cable    -   52: marker member    -   60: image capturing unit    -   70: sensor    -   M: subject    -   M1: cervical portion    -   M2: carotid artery    -   H: hand    -   P: two-dimensional ultrasound image    -   V: three-dimensional ultrasound image    -   VA1, VA2: three-dimensional ultrasound image after suppression        processing    -   VO1, VO2: three-dimensional ultrasound image    -   VG: combined three-dimensional ultrasound image    -   α: angle

What is claimed is:
 1. A three-dimensional ultrasound image generationapparatus comprising a processor, the processor configured to: acquire aplurality of two-dimensional ultrasound images from each of a firstviewpoint and a second viewpoint by imaging a target organ in a subjectat a plurality of imaging positions while moving an ultrasound probe inone direction along a body surface of the subject, the plurality oftwo-dimensional ultrasound images being acquired by performing imagingat the plurality of imaging positions from each of at least twoviewpoints of the first viewpoint and the second viewpoint; acquire, foreach imaging, position information including an imaging directionindicating a direction of the viewpoint of the ultrasound probe and theimaging position for each viewpoint; generate three-dimensionalultrasound images from each of the first viewpoint and the secondviewpoint based on the plurality of two-dimensional ultrasound imagesfrom each of the first viewpoint and the second viewpoint and theposition information for each imaging; extract the organ included in thethree-dimensional ultrasound images based on at least onethree-dimensional ultrasound image among the three-dimensionalultrasound images from each of the first viewpoint and the secondviewpoint; extract an unclear image region from the three-dimensionalultrasound image from which at least the organ is extracted among thethree-dimensional ultrasound images from each of the first viewpoint andthe second viewpoint, based on position information of the organ and theposition information of the ultrasound probe, and perform suppressionprocessing of suppressing unclearness in the extracted image region; andgenerate a combined three-dimensional ultrasound image by combining thethree-dimensional ultrasound images from two viewpoints of the firstviewpoint and the second viewpoint, the three-dimensional ultrasoundimage on which the suppression processing is performed being included inthe three-dimensional ultrasound images from at least one viewpointamong the three-dimensional ultrasound images from the two viewpoints.2. A three-dimensional ultrasound image generation apparatus comprisinga processor, the processor configured to: acquire a plurality oftwo-dimensional ultrasound images from each of a first viewpoint and asecond viewpoint by imaging a target organ in a subject at a pluralityof imaging positions while moving an ultrasound probe in one directionalong a body surface of the subject, the plurality of two-dimensionalultrasound images being acquired by performing imaging at the pluralityof imaging positions from each of at least two viewpoints of the firstviewpoint and the second viewpoint; acquire, for each imaging, positioninformation including an imaging direction indicating a direction of theviewpoint of the ultrasound probe and the imaging position for eachviewpoint; extract the organ included in the two-dimensional ultrasoundimages based on at least one two-dimensional ultrasound image among theplurality of two-dimensional ultrasound images from at least oneviewpoint of the first viewpoint or the second viewpoint; extract anunclear image region from each of the plurality of two-dimensionalultrasound images corresponding to the viewpoint of the two-dimensionalultrasound image from which at least the organ is extracted among thetwo-dimensional ultrasound images from each of the first viewpoint andthe second viewpoint, based on position information of the organ and theposition information of the ultrasound probe, and perform suppressionprocessing of suppressing unclearness in the extracted image region;generate three-dimensional ultrasound images from two viewpoints of thefirst viewpoint and the second viewpoint based on each of the pluralityof two-dimensional ultrasound images from two viewpoints of the firstviewpoint and the second viewpoint, the two-dimensional ultrasound imageon which the suppression processing is performed being included in thetwo-dimensional ultrasound images from at least one viewpoint among thetwo-dimensional ultrasound images from two viewpoints; and generate acombined three-dimensional ultrasound image by combining thethree-dimensional ultrasound images from two viewpoints of the firstviewpoint and the second viewpoint.
 3. The three-dimensional ultrasoundimage generation apparatus according to claim 1, wherein the processoris configured to extract the unclear image region based on a travelingdirection of an ultrasound wave emitted from the ultrasound probe to theorgan, the traveling direction of the ultrasound wave being derivedbased on the position information of the organ extracted and theposition information of the ultrasound probe.
 4. The three-dimensionalultrasound image generation apparatus according to claim 2, wherein theprocessor is configured to extract the unclear image region based on atraveling direction of an ultrasound wave emitted from the ultrasoundprobe to the organ, the traveling direction of the ultrasound wave beingderived based on the position information of the organ extracted and theposition information of the ultrasound probe.
 5. The three-dimensionalultrasound image generation apparatus according to claim 3, wherein theprocessor is configured to extract, as the unclear image region, aregion in which an angle formed by the traveling direction of theultrasound wave and an outer front surface of the organ is equal to orsmaller than a predetermined threshold value.
 6. The three-dimensionalultrasound image generation apparatus according to claim 4, wherein theprocessor is configured to extract, as the unclear image region, aregion in which an angle formed by the traveling direction of theultrasound wave and an outer front surface of the organ is equal to orsmaller than a predetermined threshold value.
 7. The three-dimensionalultrasound image generation apparatus according to claim 1, wherein thesuppression processing is processing of decreasing a pixel value of theunclear image region to be relatively lower than pixel values of otherregions.
 8. The three-dimensional ultrasound image generation apparatusaccording to claim 2, wherein the suppression processing is processingof decreasing a pixel value of the unclear image region to be relativelylower than pixel values of other regions.
 9. The three-dimensionalultrasound image generation apparatus according to claim 1, wherein theprocessor is configured to perform averaging processing of averagingpixel values of pixels at the same positions based on thethree-dimensional ultrasound image from two viewpoints of the firstviewpoint and the second viewpoint, the averaging processing beingprocessing of averaging the pixel values of regions other than theunclear image region on which the suppression processing is performed.10. The three-dimensional ultrasound image generation apparatusaccording to claim 2, wherein the processor is configured to performaveraging processing of averaging pixel values of pixels at the samepositions based on the three-dimensional ultrasound image from twoviewpoints of the first viewpoint and the second viewpoint, theaveraging processing being processing of averaging the pixel values ofregions other than the unclear image region on which the suppressionprocessing is performed.
 11. The three-dimensional ultrasound imagegeneration apparatus according to claim 1, the processor is furtherconfigured to: cause a display to display at least one image of thetwo-dimensional ultrasound image or the three-dimensional ultrasoundimage, wherein the processor is configure to control the display todisplay the combined three-dimensional ultrasound image, and controlsthe display to display the two-dimensional ultrasound images which areimaged at imaging positions closest to a position designated by a useron the combined three-dimensional ultrasound image which is displayed.12. The three-dimensional ultrasound image generation apparatusaccording to claim 2, the processor is further configured to: cause adisplay to display at least one image of the two-dimensional ultrasoundimage or the three-dimensional ultrasound image, wherein the processoris configured to control the display to display the combinedthree-dimensional ultrasound image, and controls the display to displaythe two-dimensional ultrasound images which are imaged at imagingpositions closest to a position designated by a user on the combinedthree-dimensional ultrasound image which is displayed.
 13. Thethree-dimensional ultrasound image generation apparatus according toclaim 1, further comprising: a marker member that is fixed to theultrasound probe; and an image capturing unit that captures an image ofthe ultrasound probe and the marker member within the same imagecapturing range, wherein the processor is configured to acquire theposition information of the ultrasound probe based on a captured imageof the ultrasound probe and the marker member which is acquired by theimage capturing unit.
 14. The three-dimensional ultrasound imagegeneration apparatus according to claim 2, further comprising: a markermember that is fixed to the ultrasound probe; and an image capturingunit that captures an image of the ultrasound probe and the markermember within the same image capturing range, wherein the processor isconfigured to acquire the position information of the ultrasound probebased on a captured image of the ultrasound probe and the marker memberwhich is acquired by the image capturing unit.
 15. The three-dimensionalultrasound image generation apparatus according to claim 1, furthercomprising: a six-axis sensor that is provided on the ultrasound probe,wherein the processor is configured to acquire the position informationof the ultrasound probe based on output information which is output fromthe six-axis sensor.
 16. The three-dimensional ultrasound imagegeneration apparatus according to claim 1, further comprising: a markermember that is fixed to the ultrasound probe; a six-axis sensor that isprovided on the ultrasound probe; and an image capturing unit thatcaptures an image of the ultrasound probe and the marker member withinthe same image capturing range, wherein the processor is configured toacquire the position information of the ultrasound probe based on acaptured image of the ultrasound probe and the marker member and outputinformation which is output from the six-axis sensor.
 17. Athree-dimensional ultrasound image generation method comprising:acquiring a plurality of two-dimensional ultrasound images from each ofa first viewpoint and a second viewpoint by imaging a target organ in asubject at a plurality of imaging positions while moving an ultrasoundprobe in one direction along a body surface of the subject, theplurality of two-dimensional ultrasound images being acquired byperforming imaging at the plurality of imaging positions from each of atleast two viewpoints of the first viewpoint and the second viewpoint;acquiring, for each imaging, position information including an imagingdirection indicating a direction of the viewpoint of the ultrasoundprobe and the imaging position for each viewpoint; generatingthree-dimensional ultrasound images from each of the first viewpoint andthe second viewpoint based on the plurality of acquired two-dimensionalultrasound images from each of the first viewpoint and the secondviewpoint and the acquired position information for each imaging;extracting the organ included in the three-dimensional ultrasound imagesbased on at least one three-dimensional ultrasound image among thethree-dimensional ultrasound images from each of the first viewpoint andthe second viewpoint; extracting an unclear image region from thethree-dimensional ultrasound image from which at least the organ isextracted among the three-dimensional ultrasound images from each of thefirst viewpoint and the second viewpoint, based on position informationof the extracted organ and the acquired position information of theultrasound probe, and performing suppression processing of suppressingunclearness in the extracted image region; and generating a combinedthree-dimensional ultrasound image by combining the three-dimensionalultrasound images from two viewpoints of the first viewpoint and thesecond viewpoint, the three-dimensional ultrasound image on which thesuppression processing is performed being included in thethree-dimensional ultrasound images from at least one viewpoint amongthe three-dimensional ultrasound images from the two viewpoints.
 18. Athree-dimensional ultrasound image generation method comprising:acquiring a plurality of two-dimensional ultrasound images from each ofa first viewpoint and a second viewpoint by imaging a target organ in asubject at a plurality of imaging positions while moving an ultrasoundprobe in one direction along a body surface of the subject, theplurality of two-dimensional ultrasound images being acquired byperforming imaging at the plurality of imaging positions from each of atleast two viewpoints of the first viewpoint and the second viewpoint;acquiring, for each imaging, position information including an imagingdirection indicating a direction of the viewpoint of the ultrasoundprobe and the imaging position for each viewpoint; extracting the organincluded in the two-dimensional ultrasound images based on at least onetwo-dimensional ultrasound image among the plurality of acquiredtwo-dimensional ultrasound images from at least one viewpoint of thefirst viewpoint or the second viewpoint; extracting an unclear imageregion from each of the plurality of two-dimensional ultrasound imagescorresponding to the viewpoint of the two-dimensional ultrasound imagefrom which at least the organ is extracted among the two-dimensionalultrasound images from each of the first viewpoint and the secondviewpoint, based on position information of the extracted organ and theacquired position information of the ultrasound probe, and performingsuppression processing of suppressing unclearness in the extracted imageregion; generating three-dimensional ultrasound images from twoviewpoints of the first viewpoint and the second viewpoint based on eachof the plurality of two-dimensional ultrasound images from twoviewpoints of the first viewpoint and the second viewpoint, thetwo-dimensional ultrasound image on which the suppression processing isperformed being included in the two-dimensional ultrasound images fromat least one viewpoint among the two-dimensional ultrasound images fromtwo viewpoints; and generating a combined three-dimensional ultrasoundimage by combining the generated three-dimensional ultrasound imagesfrom two viewpoints of the first viewpoint and the second viewpoint. 19.A non-transitory computer readable recording medium storing athree-dimensional ultrasound image generation program performing thethree-dimensional ultrasound image generation method according to claim17.
 20. A non-transitory computer readable recording medium storing athree-dimensional ultrasound image generation program performing thethree-dimensional ultrasound image generation method according to claim18.